Quick question on what part this is

Discussion in 'General Electronics Chat' started by JJS1234, Jun 9, 2011.

  1. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0
    Hello everyone. I had a quick question. I bought a broken tv on purpose (ns-ltdvd26-09) :eek: to fix it. I belive I found the problem im just not sure what this part is called.

    I also was wondering if you guys might know what #### was on it? Or the missing one was anyway... maybe an A or a R?

    http://i79.photobucket.com/albums/j160/RISEOFNATIONSFRK/DSCN2031.jpg

    http://i79.photobucket.com/albums/j160/RISEOFNATIONSFRK/DSCN2030.jpg

    and how I found it... the plastic got scorched...

    http://i79.photobucket.com/albums/j160/RISEOFNATIONSFRK/DSCN2033.jpg


    By the way, I read another thread on this forum about someone trying to fix a tv aswell, same manufacturer here and didn't know if the problem their was the same or not?

    Thanks guys!
     
  2. #12

    Expert

    Nov 30, 2010
    16,261
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    I would guess that RS3 is a 2.2 ohm resistor, but you didn't mention any labels on the board. R1 doesn't have any evidence left. I guess this is what schematics are for.

    and while we're at it, resistors rarely commit suicide. You will need to find out WHY a resistor erupted like that.

    as for the TV fixin' thread...14 months in and it is not fixed!

    ps, TV's drive me nuts. I quit fixing them about 35 years ago and they didn't get easier after that. Good luck.
     
  3. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0
    Question:

    I have some 220ohm .25w 5% tolerance resistors.

    When you say 2.2ohm do you mean 220ohm? Kinda confused. :(


    Haha, thought it would be easy. I figured that since most tvs have crappy capacitors any problems would be that. And any easy fix too. Well I got lucky once.

    I may be able to trick some ebay people to showing me a high def picture of the back so I can see what it should look like and get the #s of that.
     
  4. #12

    Expert

    Nov 30, 2010
    16,261
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    When I say "2.2" I don't mean 22 or 220
    When I say "10", I don't mean 100 or 1000.

    Does this clear it up for you?
     
  5. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    No 220 ohms is 100 times greater than 2.2 ohms resistor,so they are not same.
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
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    :mad: I don't think I want to help someone who might be tricking me. :(
     
  7. Enforcer83

    Member

    Oct 29, 2010
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    0
    You're right, it is 2.2 ohm. Usually, the "R" is used as the place holder for a decimal place both on parts and on schematics, especially schematics developed in countries other than the US, most of the time.

    The reason for doing this and why it is used as a convention for specifying a decimal place (along with k, M, G, T, μ, n, p, f) in schematics is so the decimal place is not lost. Often when reading a schematic, as an example, 4.7μF can be confused for 47μF if the type is small enough, or if you are one of our elder posters who don't have good eyes to begin with. :D

    I am guessing, from the picture, Q1 is no longer usable either, but i can't be certain. To replace that, you might need the schematic. Check to see what else in the vicinity is also connected to the resistor.

    Example of common SMD resistor markings:

    3R3 = 3.3
    220 = 22 * 10^0 = 22 ohm
    222 = 22 * 10^2 = 22 * 100 = 2.2k or 2k2

    first number is the tens place, second the ones, third the multiplier (except as in 3R3)
     
    Last edited: Jun 9, 2011
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Well, RS1 and RS2 are both definitely 2R20, or 2.2 Ohms - but RS3 appears to have been a different value. My best guess on the last two digits is "17", but no idea what was to the left of it.

    Looks like R1 is toasty, too. If I had to guess what went wrong I'd say that Q1 became shorted; as to what Q1 actually IS (besides being a transistor or MOSFET) will require a schematic.

    You might try using some 90% or better isopropyl alcohol and a soft nylon brush to clean the residue off the parts & board. You can get 99% pure isopropyl at good hardware stores. Wal-Mart sells 90% isopropyl alcohol in the health products area for a couple of bucks. Don't use lower concentrations; too much water in it, and don't leave the bottle open any longer than necessary, as it absorbs moisture from the atmosphere.

    You might see if a Sams Publishing Photofact is available; their website is here:
    https://www.samswebsite.com/

    Most of their schematics cost between $15 and $30 each. I've found them to be very helpful.
     
  9. tom66

    Senior Member

    May 9, 2009
    2,613
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    You get lucky sometimes.

    What were the symptoms of the failure? No power? I would warn against buying a TV with absolutely no power. One with standby power, but no main power - that's usually an easy fix as the primary is usually good. (Shorted FETs tend to blow fuses, which meets standby goes bad.) I chanced it paying £25 for a TV with no power, but I wouldn't do that often. Good symptoms to look for are clicking occasionally, turning on after 5 mins, or flickering backlight.

    If a TV is easily fixed, don't try and rip off someone by buying it off them for £10 when you know that they are losing. Someone who dropped the TV off at the dump in my case made a conscious choice that they couldn't care any more.
     
  10. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0
    Hey guys thanks for the reply. Im actually using somebody else s computer at the moment.

    I believe I found the correct resistors. The LCD was well not in that great of shape. I will post pictures later but on the frame their were some bad scratches. I offered $30 for it and got it at that price. The fact that I wanted to ask an eBay seller for a high rez picture in the area I was looking at I figured they would rather have me buy a new part $70. So it wasn't actually trickery :rolleyes: just not giving the whole picture.


    Thanks for the reply about the R signifying a place holder. Funny how the R was the part that burned off on all 4 resistors so naturally I thought it was either an A or an R but Google says their is no such thing as a 2A20 resistor so I was left with 2R20 and luckly their is some.

    2.20ohm Resistor 1/2w OR 1w (not sure which one to pick) at 1% tolerance.

    The other is 2R0: 2ohm 1/4w 1% tolerance.


    I would guess that the wattage of the resistor above would be 1/4w since the only thing separating the 2.0ohm and 2.20ohm is a transistor.



    See if I can find these. Thanks for the reply and well, im a noob at this and taking time to help me. :)



    I was looking online for the part but although all the specs match their is one I have no idea about. Voltage. The ones that I can find are either 200v or 250v. Im not sure what voltage to pick.
     
    Last edited: Jun 12, 2011
  11. #12

    Expert

    Nov 30, 2010
    16,261
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    Measure the resistors very closely. The size is a clue about their wattage and voltage.
     
  12. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    I guess that since RS1 to RS3 are all in parallel, and even the name implies they are shunt resistors, so they all should have the same value.
     
  13. tom66

    Senior Member

    May 9, 2009
    2,613
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    From the size it looks like a 1206 SMD resistor. Usually 1/3W to 1/2W rated power dissipation.

    If the resistors are shunt resistors then their voltage drop will be low. In parallel they make 0.73 ohms. The transistor might be part of an over-current shut down circuit. If it is an NPN which conducts at around BE = 650mV, then it might make the current shut down occur at around 900mA. Alternatively, it could be compensation for increasing load e.g. switching on a fan (if any) or switching modes from PPM to PWM, in some kinds of buck converter, which gets lower ripple but at the expense of efficiency.

    I wonder if the resistor is really burnt. It could be that it came out like that at the factory or the marking is a result of poorly applied glue which has aged due to heat. Such a resistor is unlikely to fail unless significantly overloaded. Assuming 1/3W each, that array could tolerate 1W for its entire life time. (Read the datasheet on 1206 carbon film SMD resistors: the spec often states 1/3W continuous up to a maximum ambient temperature of 85°C, which is likely to be okay in that TV.) 1W means that the current through them must have been (according to I^2 * R) about 1.17A. So why wouldn't said overload protection already be acting? Seems that something else must have gone wrong to allow this failure, if it is the case. Looking at the other resistor, R1, which might be a collector or emitter resistor, that has also failed; which could mean that it was conducting a large current. That would make the NPN suspect. Perhaps the voltages on the board went crazy (maybe due to bad caps) which fried the lot? In which case, repair may be very difficult. :(

    Measure the resistor array - you should measure from 0.6 - 0.8 ohms.
     
    Last edited: Jun 12, 2011
  14. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0

    Will do when I get back home. Ill check on the power-board and post some pictures of the entire thing. The TV has no power at all so I assume the resistors are apart of the main circuit. No standby light- no nothing.

    I did find the correct resistor for one of them. The closest I could find without shelling out $20 for shipping had a different tolerance of 5% instead of 1%.

    About the capacitors...

    I didn't see any bulging ones however their is a large one on its side with some sort of plastic protection cap thing on the top. If it was say bad, and bulging would it show it? Hard to describe.


    http://i79.photobucket.com/albums/j160/RISEOFNATIONSFRK/DSCN2026.jpg

    http://i79.photobucket.com/albums/j160/RISEOFNATIONSFRK/DSCN2025.jpg

    If your thinking the caps went bad, none of the ones I can see look bad, perhaps the large one 450v (??uF) I will take better pictures when I get back home.
     
    Last edited: Jun 12, 2011
  15. tom66

    Senior Member

    May 9, 2009
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    The 450V ones are usually okay... it's the lower voltage ones you want to be wary of.
     
  16. SgtWookie

    Expert

    Jul 17, 2007
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    The HV capacitors can fail internally and still look OK on the outside - but cause other parts of the circuit to burn up.

    My wife found a TV on the curb last year, and brought it home just for grins. There was a fried resistor, but everything else looked OK. I discovered that a 220uF 200v cap had failed internally; one of the leads had separated from the plates. The failed cap caused a high amount of current to flow through the resistor which would normally only have occurred during power-on. Replaced the cap and the resistor, and the problem was cured.
     
  17. tom66

    Senior Member

    May 9, 2009
    2,613
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    When the big filter bulk capacitors fail they usually lose capacitance or have increased ESR. Both lead to greater ripple. That cap might have 10 or 20V of ripple across it which is tolerable but if it starts getting 50V across it, the circuit might brown out (so nothing works), or worse - the output rails will ripple, causing bizarre glitches (for example, TV will work when the volume is low, turning it up will cause the picture to go black, or something like that...) You can pull your hair out trying to figure these things out!
     
  18. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0
    So I suppose we are settling on that one of the capacitors has died. I dont think I have any way to test them let alone even if I did, the circuits that fried need to be replaced for any power to go through the board. So I should just replace them all? Its cheap to do so, but I will take a look more closely to be sure.

    I may have missed a circuit, maybe another is fried too. I was in a hurry and the burn pattern on the plastic gave it away.

    Question from above...

    Do I need to match the tolerances of one of the resistors. I believe it is a 1% tolerance and is it possible or bad to replace with a 5%?


    Nevermind found the fuse. Going to test...
     
    Last edited: Jun 13, 2011
  19. tom66

    Senior Member

    May 9, 2009
    2,613
    213
    Nah, I'd say from the failure mode, the cap is the least of your concerns... It'll be a few $ to replace.

    Replace the resistors with 1%. Buy them here:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RL16R2.2FCT-ND

    $0.61/ea (min order 10) plus shipping of a few bucks...
     
  20. JJS1234

    Thread Starter Member

    May 26, 2011
    41
    0
    I dont know if this is any different than above but perhaps another symptom??

    I had the lights off and I could see mini sparks in the defective resistors.

    And the voltimeter I was using could detect these, fluctuating I believe (don't remember)75-120v.


    EDIT: Ok just purchased both resistors and a cap, I have one in my stereo that seems a little corroded on the top. :O
     
    Last edited: Jun 14, 2011
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